In communications satellites, input signals that are encoded in a plurality of frequencies are received via an input antenna, further processed, and usually emitted in another direction via an output antenna. In order to further process the signals, the received frequencies are split into frequency bands, for example, by means of bandpass filters, amplified, and recombined.
As a rule, these filters operate in the microwave range and must normally be able to process high-output signals with small losses. For example, waveguide filters may be used for this purpose in which a plurality of cavity resonators that are adjusted to the frequency band are coupled in series. Here, the cavity resonators are connected to one another via coupling irises (i.e., openings having a diameter that is smaller than the volume of the cavity resonators) that determine the width of the passband.
The bandwidth of a microwave filter is primarily a function of the quantity of the energy coupling between the resonators. In a typical waveguide filter arrangement, the portion of the coupling energy is determined by the size of the coupling iris between the resonators.